Because of a tendency of high density and high definition of a semiconductor element, development of a higher microfabrication technique is demanded in recent years. Conventionally, in manufacturing of a semiconductor integrated circuit device (hereinafter, also referred to as a semiconductor device), planarization of an interlayer insulation film, a copper-embedded wiring, or the like has been carried out by using chemical mechanical polishing (hereinafter, referred to as CMP), in order to prevent a problem that unevenness (level difference) of a layer surface exceeds a depth of focus of lithography and hampers obtaining a sufficient resolution. Importance of such planarization by CMP increases all the more as demand for high resolution or miniaturization of a semiconductor element becomes severer.
Further, in manufacturing of a semiconductor device, a isolation method (shallow trench isolation, hereinafter, referred to as STI) by a shallow trench with a small element isolation width is introduced in recent years in order to advance more sophisticated miniaturization of a semiconductor element.
STI is a technique to form an electrically insulated element region by forming a trench in a silicon substrate and embedding an insulation film in the trench. In STI, first, as shown in FIG. 1A, after an element region of a silicon substrate 1 is masked by a silicon nitride film 2 or the like, a trench 3 is formed in the silicon substrate 1 and an insulation film such as a silicon oxide film 4 or the like is deposited to fill the trench 3. Next, by CMP, the silicon oxide film 4 on the silicon nitride film 2 being a convex part is polished and removed while the silicon oxide film 4 in the trench 3 being a concave part is left, whereby an element isolation structure in which the silicon oxide film 4 is embedded in the trench 3 is obtained as shown in FIG. 1B. In CMP as above, by a configuration where a selectivity (polishing rate of silicon oxide film/polishing rate of silicon nitride film) between a polishing rate of the silicon oxide film 4 and a polishing rate of the silicon nitride film 2 is made sufficiently high so that polishing may finish at a time that the silicon nitride film 2 is exposed, a smoother surface can be obtained.
In manufacturing of a semiconductor device, other than planarization of the silicon oxide film in STI as above, CMP is carried out by using a polishing agent which contains abrasive particles of fumed silica, colloidal silica, alumina, ceria (cerium oxide) or the like, in order to planarize an insulation film of a silicon oxide or a ferroelectric film for capacitor formed by various methods such as plasma-CVD (chemical vapor deposition), low pressure-CVD, sputtering, and electroplating. As miniaturization and high definition of an element advances, a defect (hereinafter, referred to as a polishing defect) formed in an interlayer insulation film or an insulation film for STI at a time of polishing becomes increasingly a large problem, since the defect causes wiring short circuit or the like and leads to reduction of a yield.
Conventionally, when a surface to be polished is an insulation film made of a silicon oxide or the like, a polishing agent which contains high-purity cerium oxide particles have been used since the high-purity cerium oxide particles have lower hardness compared with silica-based abrasive particles and hard to cause a polishing defect (refer to JP-A 2000-109803, for example).
However, in response to further miniaturization of a semiconductor integrated circuit, demand for prevention of a polishing defect becomes further higher, and the polishing agent described in JP-A 2000-109803 cannot sufficiently respond to such demand. Thus, it is proposed that a particle diameter of a cerium oxide being an abrasive particle should be made smaller (refer to JP-A H08-081218, for example). However, when cerium oxide particles with a small particle diameter are used as abrasive particles, a polishing rate is reduced, and there is a problem that an efficiency of polishing operation is significantly worsened.